X-ray tubes are extremely valuable tools that are used in a wide variety of applications, both industrial and medical. An x-ray tube typically includes a cathode and an anode positioned within an evacuated enclosure. The cathode includes an electron source and the anode includes a target surface that is oriented to receive electrons emitted by the electron source. During operation of the x-ray tube, an electric current is applied to the electron source, which causes electrons to be produced by thermionic emission. The electrons are then accelerated toward the target surface of the anode assembly by applying a high-voltage potential between the cathode assembly and the anode assembly. When the electrons strike the anode assembly target surface, the kinetic energy of the electrons causes the production of x-rays. The x-rays are produced in an omnidirectional fashion where the useful portion ultimately exits the x-ray tube through a window in the x-ray tube, and interacts with a material sample, patient, or other object with the remainder being absorbed by other structures including those whose specific purpose is absorption of x-rays with non-useful trajectories or energies.
The target surface of the x-ray tube anode is generally angled, or otherwise oriented, so as to maximize the amount of x-rays produced at the target surface that can exit the x-ray tube via the window. Notwithstanding the orientation of the anode target surface, some errant x-rays nonetheless emanate in various directions from the target surface. Further, some electrons back scatter off of the target surface and strike other surfaces within the x-ray tube, which sometimes results in the production of additional errant x-rays. Thus, while some x-rays do exit through the window and are utilized as intended, other errant x-rays do not exit through the window. Errant x-rays that do not pass through the window often penetrate instead into other areas of the x-ray tube, where the errant x-rays may, undesirably, be transmitted through other x-ray tube surfaces if sufficient measures to prevent the escape of errant x-rays are not taken.
The escape of errant x-rays from an x-ray tube is undesired as such x-rays can represent a significant source of x-ray exposure to x-ray tube surroundings. For instance, errant x-rays can result in transmission of a relatively high level of radiation to an x-ray tube operator. In addition, errant x-rays can interfere with the imaging x-ray stream that is transmitted through the window. Such interference may compromise the quality of the images obtained with the x-ray device. For example, errant x-rays can impinge upon areas of the x-ray subject and interfere with the image being sought. The resulting interference may be manifested as clouding in the image.
While the problem of errant x-rays can be realized throughout the tube environment, certain areas of the x-ray tube are especially susceptible to the impingement of errant x-rays. For example, various devices in an x-ray tube are formed from electrically insulating materials, such as silicon glasses or alumina ceramics, that are not effective at shielding x-rays. Such electrically insulating devices may be employed, for example, in connection with a high-voltage cable that supplies high-voltage electrical power to the x-ray tube. As errant x-rays emanate directly or indirectly from the target surface toward an electrically insulating device, x-rays typically pass through the electrically insulating device without being absorbed, thus necessitating supplemental shielding around the electrically insulating device, either inside the x-ray tube or external to the x-ray tube.
The addition of supplemental shielding to an x-ray tube can be problematic however. For example, while supplemental shielding can be effective at absorbing x-rays, the supplemental shielding, which is often made of lead for example, can be relatively heavy and substantially adds to the weight of the x-ray tube. This factor becomes important in applications where a relatively low x-ray tube weight is desired or even required. Further, the addition of supplemental shielding can represent a significant cost in time and labor during x-ray tube manufacture.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.